<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>画盒子</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .header {
            height: 80px;
            background-color: black;
        }

        .nav {
            width: 1000px;
            height: 60px;
            background-color: skyblue;
        }

        .main {
            width: 1000px;
            height: 1000px;
            background-color: red;
        }

        .footer {
            height: 150px;
            background-color: green;
        }

        .center {
            margin: 0 auto;
        }
    </style>
</head>

<body>
    <div class="header"></div>
    <div class="nav center"></div>
    <div class="main center"></div>
    <div class="footer"></div>
</body>

</html>